Promising new directions currently under development should result in considerable advances in our understanding of the modes of action and the metabolic roles of various carbonic anhydrases. These branch off points involve the following projects: (1) Kinetics and mechanistic characterization of novel mammalian carbonic anhydrases isolated from skeletal and heart muscles, as well as of microbial carbonic anhydrase recently discovered in E. coli. (2) Exploration of additional analog reactions, bifunctional substrates and specific sulfonamide inhibitors. New reactions which deserve special mention are hydrations of imines and epoxides; hydrolyses of acid anhydrides, lactones, acyl phosphates and cyclic phosphate esters; and certain analog decarboxylation reactions. Among new bifunctional substrates, mention should be made of glyoxylic, alpha-ketobutyric, alpha-ketoglutaric, alpha-ketoglutaramic and oxaloacetic acids as well as of 3-phosphoglyceraldehyde. (3) Investigation of the catalytic properties of recently detected complexes between carbonic anhydrase and other proteins. This is new area where answers are urgently needed to clarify the role of carbonic anhydrase in the following tissues: erythrocyte (complexes with deoxy- and oxyhemoglobin), muscles (complexes with lactate and 3-phosphoglyceraldehyde dehydrogenases), and liver (complexes with alcohol and aldehyde dehydrogenases). (4) Solvent proton T1 measurements designed to test the presence of a fifth coordination site at the active site of Co(II) carbonic anhydrase. Also, measurements of paramagnetic enhancement of longitudinal relaxation of H13 CO minus 3, CH313CHO, CH313COCO2 minus and CH3CO13CO2 minus in Co(II)-carbonic anhydrases to delineate the conformations of these substrates when bound to the enzyme. (5) Systematic stop-flow, T-jump, nmr (1h and C13) and O18-exchange studies of various native, Co(II)- and Mn(II)- carbonic anhydrases and of active site modified enzymes. (6) New studies pertaining to the role of plant carbonic anhydrase in photosynthesis. Investigation of complexes with (1) H2PO4 minus/HPO4 minus, (2) organic phosphate anions involved in the Calvin cycle, and (3) glycollate oxidase. (7) Exploratory studies of enzymes obtained from mutants of E. coli and Neisseria Sicca, resistant to sul (Text Truncated - Exceeds Capacity)